Both potable water and wastewater contain microorganisms. Various water treatment systems are provided in the prior art for destroying bacteria and other microorganisms from potable water and disinfecting the water to a level suitable for human and animal consumption. Other water treatment systems treat wastewater by reducing the infectious components to levels which are not suitable for human or animal consumption, but are satisfactory for discharge into various water bodies. Similar water disinfection systems may be applied in both potable water and wastewater applications to reduce the microbial containment level to certain specified governmental standards. Historically, the use of chlorination for disinfection has been pervasive, and in recent years systems employing ultraviolet radiation and ozonation have been commercialized as well.
Various prior art electrochemical processing systems have also been used for disinfection and/or oxidation of potable water and wastewater. These prior art systems include electroporation and electrolytic systems.
Electroporation systems have been used for the inactivation of bacteria from water including wastewater. The technique is generally based on increasing cell membrane permeability using very high voltage electric fields. The water is passed through a disinfection unit having spaced electrodes which are connected to a high voltage source, generally on the order of kilovolts. The high electric field generated changes the permeability of microbial cells and creates a transient, reversible and/or a permanent and irreversible state of increased porosity. The transient condition usually arises at lower values of electric field intensities. The permanent and irreversible state thus is generally operable at much higher levels. Although such systems have been developed, the required high voltage power supply is very costly and also may raise serious safety problems. Electroporation disinfection systems also consume large amounts of electric power. Electroporation systems have disadvantages not only from the cost, but also from the practicality of the system as applied to large water utility and wastewater applications. Further, requirements for large flow cells within closed systems or open channels limit the current state of the art in electroporation systems.
Electroporation employs the use of high voltage pulsed or DC electric fields previously discussed for disinfection is practical only in small, point-of-use applications. For example, the use of prior art treatment with electric fields in the one to ten kilovolt per centimeter range extrapolates to tens, possibly hundreds of thousands of volts required using the water flow routes of existing treatment plants. At the treatment plant level, voltage values and power consumption are significantly large and raise concerns for both safety and cost effectiveness.
DC-based electroporation (Electric Arcing) employs high voltage pulses that destroy microbial cells by increasing cell porosity and permeability. DC-based electroporation is a high-voltage process. DC electroionics electrically generates hydrogen peroxide and other oxidizing agents with direct current-activated electrode action. Both of these DC techniques are characterized by efficient disinfection in small laboratory-scale processes, inefficient disinfection in large-scale processes, and significant electrode contamination after prolonged operation. Both technologies are not efficient or cost-effective in large-scale plant-size operations.
Electrolytic systems employ electrolytic cells that rely on the use of metal electrodes which increase metal concentrations in aqueous solution that sometimes exceed maximum contamination levels for silver, copper, lead or other metals. This toxicity problem has been generally ignored or presented generally without a proper basis for solving the problem particularly in high flow rate systems by most of the prior art, except for U.S. Pat. No. 3,936,364, which provides a second electrolytic cell to remove the toxic metal. The '364 patent, however, does not establish that such metal removal could be accomplished in a cell of reasonable and cost effective size, particularly in high flow rates systems.
The prior art electromagnetic field approaches to wastewater disinfection and/or organics oxidation have failed to achieve the required efficiency levels in large-scale disinfection operations. DC-based systems are also susceptible to electrode contamination. Electroporation systems have found use only in limited, point-of-use applications where small pipe diameters are the rule. However, commercially applicable systems for water treatment plants and large-scale wastewater processing have not found significant application.
Alternate systems based on ionic current flow within water have been used, particularly for limited flow systems such as swimming pools and other like bodies. These systems, however, use metals such as zinc, copper, lead, silver or the like which introduce toxic ions into the water. This approach raises further questions or acceptability and compliance with federal and state chemical contamination limits.
In summary, the prior art has considered the problems of disinfecting water with various electroporative or ionic processes to establish a level acceptable for human or animal consumption and of wastewater for discharge into large bodies of water. It is submitted that such suggested systems cannot operate at the flow rate in channel or pipe sizes required for municipal water/wastewater treatment plants or other high volume applications. Further, the prior ionic disinfection art has universally relied on metal electrodes which introduce undesirable and significant toxic metals into the treated water system, and particularly systems which would not function practically in the channel or pipe sizes at the high rates of flow encountered in modern day community water and wastewater treatment systems.
Therefore, a need exists for a disinfection and oxidation system for both potable water and for wastewater which is operable to remove bacteria and other microorganisms from water and wastewater, which is operable at high rates of flow as encountered for commercial and community water supplies as well as various sizes of wastewater treatment systems.
It is also desirable to utilize as many potentially useful or valuable by-products of such improved apparatus and/or methods of treating aqueous solutions. Production of such by-products may provide an alternative consideration or reason for applying such improved apparatus and/or methods to aqueous solutions.